In vitro and in vivo insulinotropic properties of the multifunctional frog skin peptide hymenochirin-1B: A structure-activity study

Bosede O. Owolabi, Opeolu O. Ojo, Dinesh K. Srinivasan, J. Michael Conlon, Peter R. Flatt, Yasser H.A. Abdel-Wahab

Research output: Contribution to journalArticlepeer-review

24 Citations (Scopus)

Abstract

Hymenochirin-1b (Hym-1B; IKLSPETKDNLKKVLKGAIKGAIAVAKMV.NH2) is a cationic, α-helical amphibian host-defense peptide with antimicrobial, anticancer, and immunomodulatory properties. This study investigates the abilities of the peptide and nine analogues containing substitutions of Pro5, Glu6, and Asp9 by either l-lysine or d-lysine to stimulate insulin release in vitro using BRIN-BD11 clonal β cells or isolated mouse islets and in vivo using mice fed a high-fat diet to produce obesity and insulin resistance. Hym-1B produced a significant and concentration-dependent increase in the rate of insulin release from BRIN-BD11 cells without cytotoxicity at concentrations up to 1 μM with a threshold concentration of 1 nM. The threshold concentrations for the analogues were: [P5K], [E6K], [D9K], [P5K, E6K] and [E6K, D9k] 0.003 nM, [E6K, D9K] and [D9k] 0.01 nM, [P5K, D9K] 0.1 nM and [E6k] 0.3 nM. All peptides displayed cytotoxicity at concentrations ≥1 μM except the [P5K] and [D9k] analogues which were non-toxic at 3 μM. The potency and maximum rate of insulin release from mouse islets produced by the [P5K] peptide were significantly greater than produced by Hym-1B. Neither Hym-1B nor the [P5K] analogue at 1 μM concentration had an effect on membrane depolarization or intracellular Ca2+. The [P5K] analogue (1 μM) produced a significant increase in cAMP concentration in BRIN-BD11 cells and stimulated GLP-1 secretion from GLUTag cells. Down-regulation of the protein kinase A pathway by overnight incubation with forskolin completely abolished the insulin-releasing effects of [P5K]hym-1B. Intraperitoneal administration of the [P5K] and [D9k] analogues (75 nmol/kg body weight) to high-fat-fed mice with insulin resistance significantly enhanced glucose tolerance with a concomitant increase in insulin secretion. We conclude that [P5K]hym-1B and [D9k]hym-1B show potential for development into anti-diabetic agents.

Original languageEnglish
Pages (from-to)535-547
Number of pages13
JournalAmino Acids
Volume48
Issue number2
DOIs
Publication statusPublished - Feb 1 2016
Externally publishedYes

Keywords

  • Amphibian skin peptide
  • Hymenochirin-1b
  • Insulin release
  • Type 2 diabetes

ASJC Scopus subject areas

  • Biochemistry
  • Clinical Biochemistry
  • Organic Chemistry

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